Leukocyte and endothelial cell adhesion molecules are involved in critical pathways of the inflammatory response. Leukocyte adhesion deficiency is characterized by childhood presentation of indolent, recurrent infections of the skin, oropharynx, and respiratory tract. The molecular basis is defective production of CD18 leading to reduced cellular expression of leukocyte integrins. ICAM-1 is a ligand for one of the CD18 family of integrins. ICAM-1 is a member of the immunoglobulin supergene family and has been shown to play an important role in transplantation biology. In phase I of this proposal, I will join the efforts in Dr. Beaudet's laboratory aimed at obtaining murine models with mutations of CD18 and ICAM-1 to better delineate their biological functions. One germ-line mutation in CD18 has been obtained and others are being sought. I expect to be particularly involved in the introduction of mutations in the ICAM-1 gene using homologous recombination in embryonic stem (ES) cells. Mutant ES cells will be obtained using selection in tissue culture, screening with PCR, and confirmation by Southern blotting. Mutant cells will be used to establish germ-line transmission, and mutant mice will be characterized phenotypically. The effect of mutations in CD18 and ICAM-1 will be tested using transplantation with bone marrow and skin or cardiac tissue. In phase II of this project, I will focus on further biological studies of the mutant animals, and I will address the significance of potential genetic variation in these cell adhesion molecules in humans. The coding exons of CD18 and ICAM-1 will be sequenced in normal and high risk populations searching for amino acid polymorphisms of clinical significance. If found, the frequency of these amino acid polymorphisms in various clinical populations would be analyzed. Additional studies in the mice would focus on the effect of these mutations on common disease processes such as atherosclerosis, autoimmune disease, and inflammatory processes. A parallel goal of this project is preparation of the candidate for a career as an independent investigator. A series of graduate school courses focusing on cell and molecular biology will be taken for credit. An intense exposure to laboratory research is planned with 100% of time devoted to research training during the early years. The Department of Pediatrics has a long-term commitment to a faculty position in the Section of Allergy and Immunology.